The present invention relates to a multi-link system for mounting rear wheels of an automotive vehicle.
Vehicle designers have used a variety of independent suspensions for driven rear wheels of automotive vehicles. The provision of independent suspensions for rear drive wheels becomes especially complicated when it is desired to use alternatively a beam axle and an independent suspension on a common vehicle platform. And, it is desired to use both types of axles with a common vehicle floor pan in the case of unitized construction with sub-frame. In this case, commonality dictates that the spring pocket and the shock absorber upper mount be identical, or nearly so, for both types of axles. Thus, although U.S. Pat. No. 4,828,279 discloses a common type of independent suspension for a rear drive wheel of a vehicle, the system of the ""279 patent would not accommodate a centrally mounted spring and shock absorber situated in the manner of a beam axle.
The inventors of the present invention have determined that their system will produce excellent results in term of wheel control kinematics when used with a vehicle platform permitting the alternative employment of a beam axle or a fully independent rear suspension.
An independent suspension for a powered rear road wheel of an automotive vehicle includes a subframe attached to a vehicle body and a hub carrier with a wheel hub rotatably attached thereto, with the wheel hub defining the wheel center. A laterally extending lower control arm has an inner end and an outer end, with the inner end being pivotably attached to the subframe at a first attachment point leading the wheel center and at a second attachment point trailing the wheel center. The outer end of the lower control arm is pivotably attached to a lower portion of the hub carrier at a third attachment point trailing the wheel center. The lower control arm further has a fourth attachment point located at its outer end and leading the wheel center. An internal support link extends upwardly between the fourth attachment point of the lower control arm and a forward portion of the hub carrier. A laterally extending upper control arm having an inner end and an outer end is pivotably attached at its inner end at a single point to the vehicle subframe. The outer end of the upper control arm is attached to the hub carrier such that the outer end of the upper control arm lies in the transverse vertical plane containing the wheel center. Finally, a laterally extending toe link has a first end pivotably attached to the subframe at a location under the first attachment point of the lower control arm. The toe link also has a second end pivotably attached to the hub carrier in front of and below the wheel center. The toe link is preferably mounted such that it is generally horizontal at normal right height.
According to another aspect of the present invention, the subframe to which the wheel suspension is attached may comprise either a rear suspension subframe or a portion of a vehicle frame providing mounting points for both a front and a rear suspension.
According to another aspect of the present invention, the first attachment point of the lower control arm to the subframe comprises an asymmetric bushing having a lower degree of stiffness in a transverse direction and a higher degree of stiffness in a vertical direction such that the asymmetric bushing will resist moments imposed on the lower arm by the hub carrier during forward braking of the hub carrier while allowing recession of the lower arm in response to longitudinal impacts directed against the roadwheel. This bushing also assists in producing desirable compliance steer characteristics.
According to another aspect of the present invention, the outer end of the upper control arm is attached to the hub carrier at a position which is inboard of the attachment point of the lower control arm to the hub carrier such that the upper control arm is shorter in length than the lower control arm.
The present invention further includes a coil spring interposed between an upper surface of the upper control arm and the body of the vehicle, with the coil spring having a center axis passing through a line defined by the inner and outer ends of the upper control arm. Similarly, a telescoping shock absorber extends between a trailing portion of a lower control arm and the body of the vehicle.
The third attachment point of a lower control arm, which trails a wheel center, is preferably lower than the fourth attachment point of the lower control arm to the internal support link.
It is an advantage of the present independent suspension that the suspension may be packaged and used on a vehicle with a chassis capable of mounting not only an independent suspension, but alternatively, a beam type of driving rear axle.
It is a further advantage of the present invention that the geometry of this suspension exhibits excellent anti-squat and anti-lift characteristics.
It is a further advantage of the present invention that having a suspension spring on the wheel center means that no caster change occurs as the wheel is loaded and unloaded.
It is a further advantage of the present invention that the first attachment point bushing, being relatively softer in a lateral-radial direction provides longitudinal compliance, as well as controlling the compliance steer characteristics of the suspension.
Other advantages, as well as features and objects of the present invention, will become apparent to the reader of this specification.